A number of figures linked to the Obeid family have denied being part of sham purchases of coal-rich farms that stood to make the Obeids tens of millions of dollars, a corruption inquiry has heard.

On another stunning day, the Independent Commission Against Corruption (ICAC) inquiry also heard that an associate of former Labor minister Ian Macdonald tried to retrieve a legal file linked to the inquiry after Mr Macdonald told him he'd met with ICAC officers.

ICAC is investigating Mr Macdonald's decision in 2008 to open NSW's Bylong Valley to coal mining and how it benefited Labor powerbroker Eddie Obeid.

Mr Macdonald is accused of doing the bidding of Obeid family members, who allegedly hid their involvement through complex trust and company structures.

The inquiry has heard that the Obeids stood to make $100 million from mining deals in the area.

A friend of the Obeid family, Rocco Triulcio, on Thursday denied trying to hide his involvement in the purchase of a farm, Donola, in the Bylong Valley in 2008.

Mr Triulcio and his brother Rosario have a 50 per cent stake in the $600,000 farm bought with the Obeids.

The farm was owned by a trust company, Geble, whose sole director and shareholder at the time was the Obeids' solicitor, Chris Rumore.

Mr Triulcio rejected suggestions the complex ownership structure was an attempt to hide his involvement in the purchase.

He insisted he bought the farm "for leisure" even though he only visited it once in four years and had no valuation done prior to buying it.

His brother Rosario also denied being part of a sham purchase.

"You wouldn't have known whether they ran goats or rats or cows there, would you?" counsel assisting the inquiry, Geoffrey Watson, asked.

Greg Skehan, a Sydney lawyer, denied acting as a front man in another company, Voope, set up to progress the Obeids' interests in coal mining.

He said a complex arrangement under which he held the shares in Voope, described as a "clean skin" company, on trust for the Obeid family was not a move aimed at hiding their involvement in it.

The inquiry also heard evidence that John Gerathy, a long-time associate of Mr Macdonald, tried to retrieve a legal file linked to the inquiry after a call from Mr Macdonald to him around September this year.

Mr Gerathy, a lawyer, said in the call, which took place before the start of the ICAC inquiry, that Mr Macdonald told him he had been to ICAC.

After the call, Mr Gerathy said he tried to retrieve a legal file relating to legal work he did for Tianda Resources, a company the Obeids are alleged to have tried to involve in a deal about one of the Bylong Valley properties.

Mr Watson suggested Mr Gerathy's actions were the result of Mr Gerathy's involvement with Tianda potentially being related to allegations of corruption.